In recent years, several trends have been influencing the evolution of next generation mobile broadband cellular networks.
Among the major influential factors one may find the following:                (i) The fast adaptation and rollout of mobile broadband cellular networks (3G and LTE) by MNOs;        (ii) The widespread of Wi-Fi hot spots providing local high speed data broadband connectivity, and the incorporation of Wi-Fi capabilities in most of the currently used portable mobile broadband devices;        (iii) “Data explosion” which has been ramping up ever since the introduction of the iPhone® in 2007 driving the need for new methods that would allow more cost effective delivery of mobile broadband services;        (iv) The scarcity of licensed spectrum to enable provisioning of 3G/LTE data services that meet the growing demand for mobile broadband data services;        (v) The fact that most of data traffic is being generated indoors and the cellular industry trend of introducing low power, localized coverage, small cells, as an effective means for cellular network densification (aka “heterogeneous networks”);        (vi) Mobile devices evolution which enables the introduction of multi technology devices at lower cost for the end users thereby enabling simultaneous connectivity of the user equipment (UE) to both Wi-Fi and cellular networks.        
In view of these trends, 3GPP has identified the potential in having a tighter integration between native cellular service in licensed spectrum and Wi-Fi service over unlicensed spectrum, and such framework has been introduced in 3GPP R10 within the scope of ANDSF (Access Network Discovery and Selection Function) in the EPC.
The new EPC architecture introducing ANDSF is described in 3GPP Specification TS 23.401 entitled “General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access” and in 3GPP Specification TS 23.402 entitled “Architecture enhancements for non-3GPP accesses”.
FIG. 1 describes the reference architecture used by the 3GPP forum with ANDSF for trusted Wi-Fi and cellular integration. However, there are still a number of challenges that have to be overcome in order to achieve an effective and reliable Wi-Fi/Cellular integrated solution. Some of these challenges are:                a) To monitor and compare Wi-Fi vs. cellular performance at the levels of the device/cell. From the Mobile Network Operator (“MNO”) standpoint, it is desired that the user will get the best possible quality of experience (“QoE”) in accordance with the service consumed and the user priority level, under the constraints of load management.        b) To enable scalable real time localized control of device steering between cellular/Wi-Fi networks, when devices are in active mode as well as in idle mode. In order to effectively manage Wi-Fi offloading, the network is required to control millions of users, individually, according to each user varying conditions, and according to network varying local conditions. Achieving that goal in a scalable manner and without inducing a further load is yet another challenge that needs to be overcome.        c) To measure QoE in Wi-Fi network. The challenge lies primarily in the fact that there is no native reverse control channel in Wi-Fi network to be used for reporting back the QoE experienced by the user.        d) To carry out an effective divert (offload) traffic from cellular network to Wi-Fi network and to divert the traffic back from Wi-Fi network to cellular network. Different users at different locations might impose different load conditions upon the cell radio resources. For example, a user located at a cell edge is likely to load the cell more than a user located at the cell core, while both users consume the same amount of data over the same service type. The challenge therefore lies in achieving an effective offloading and diverting back policy in view of the complex radio interface realities of 3G and LTE.        e) Coordination between various Load Balancing functions and ANDSF, according to MNO policy (intra 3G/LTE, IRAT, PCC, ANDSF). It is likely that the MNO may activate simultaneously many load balancing features, such as intra/inter system load balancing and policy enforcement functions carried out by PCRF/PCEF platforms in the EPC. Overlaying ANDSF and Wi-Fi offload without ensuring suitable coupling with these methodologies might lead to non-optimal network resources utilization and actually might result in loss of revenues to the MNO due to different revenues models in Wi-Fi vs. cellular networks; and        f) Network triggered mobility procedures. Current state of the art regarding cellular and Wi-Fi integration solutions assume that when in Wi-Fi mode, mobility decisions are taken by the UE via the CM (Connection Manager). However, there might be a need for strict network control over users' mobility between the different layers. This might be required either to support delay sensitive (eg CS) applications continuity and quality in cell edge environment as well as to support Load Balancing procedures between Wi-Fi and Cellular and vice versa.        
In current cellular mobile broadband systems the achievable data rates are highly dependent on the users' positions in the network. Even though it is of great importance to deliver the same user experience across the whole cellular network in order to satisfy the users' expectations, still, a considerable gap is observed between cell-edge and cell-core performance due to inter-cell interference, which poses the main limitation of state-of-the art mobile networks.
Therefore, there is a need to improve the way cellular networks and Wi-Fi networks are integrated, and particularly the Load and Quality analysis and management when the users are steered (while being in active mode and in idle mode) between these two technologies, namely Wi-Fi and Cellular.